Its raw portrayal of poverty earned it a 15 rating by the British Board of Film Classification (BBFC). Sean had intended to put on free showings of the film in schools and community centres but insists that the rating could exclude children from watching it and limit the positive impact it could have.

The BBFC’s decision is down to the use of strong language in the documentary – there are around 20 instances – as the limit for a 12A rating is four instances of swearing. But the director has defended the language used as “culturally credible” and said: “I suspect it’s more to do with poverty than it is to do with the f-word.”

Sean told The Big Issue: “There are a few scenes where Steve is in debt and in difficulty, but it’s so far-removed from their world that they’d probably say, that’s scary, better give that a 15.

“For a documentary like this with the message it has, getting the audience once you’ve made the film is absolutely paramount and anything that stands in your way that helps get the audience is great. But I am insulted and devastated.”

The director pointed to the example of 2010 movie The King’s Speech, which was given the same rating for a scene in which King George is encouraged to swear as part of his speech therapy – before being dropped to a 12A after further reflection by the board.

The terms of a 12A classification make exceptions for strong language depending on “the manner in which it is used, who is using the language, its frequency within the work as a whole and any special contextual justification”.

DID YOU KNOW…

In total, more than 92,000 people have sold The Big Issue since 1991 to help themselves work their way out of poverty – more than could fit into Wembley Stadium.

But Sean expressed a belief that the BBFC had missed the context of the film, giving “no consideration of the content”.

He said: “What’s the ratio of value that the film can offer kids versus the danger it poses? There’s no violence, no sex, no aggression, just a bloke inspiring kids to get out and do good things in really difficult times. But no, it’s a 15 because the f-word’s used.”

The film has been rated 12A in both Hull and Sheffield – with local ratings taking precedence over national ones – so some children have already been able to view the film, describing it as “inspiring” and “empowering”.

Just got this message from a father at the screening last night who brought his kids to see @northernsouldoc “Thank you Sean McAllister. The kids were very impressed and inspired by the film. Hannah has decided to make her own film and is scripting it right now!” @BBCNewsnight

Some children also said the swearing was unnoticeable as it was just like what they hear in playgrounds or at home.

According to the director, the film team has gained the support of “every MP in the city” who have signed a letter agreeing that “the greater good of the film in its existing form serves such a strong purpose and offers kids so much more – they really want the board to reconsider. Because its current state is harmless.”

Sean, whose 2015 documentary A Syrian Love Story earned him a BAFTA nomination for Outstanding Debut By A British Writer, Director or Producer, intends to appeal the board’s decision, and has requested a formal list of all the required cuts that would identify which four uses of strong language would be suitable for a 12A rating.

Tonight I saw a screening of @northernsouldoc in Hull & very suprised that @BBFC has classified the film as a certificate 15. Really don’t understand why it merits that rating? The Kings Speech was initially given an adult rating because of swearing but was then revised to PG. pic.twitter.com/roYspSC0Nx

However, the director admitted that he is not inclined to cut moments from the film, despite insisting the British Film Institute has offered funding to help him do so. He said: “Steve carries a certain credibility because of who he is and how he is and how he speaks.

“If you feel it’s been doctored, as a viewer, you’re going to smell a rat. Or it’s going to take away from the authenticity of the film. However much I want to do it, as a documentary film maker I’m not sure.”

A BBFC spokesperson said: “While some people are less bothered by strong language than others, our own research shows that a substantial portion of the public, especially parents, do feel limits should be placed on the amount of strong language permitted at the 12A level.

“The distributor and film maker are welcome to reduce the quantity of strong language in the film in order to obtain a 12A classification.”